A common type of a radar detector device is one that monitors at least one known radar frequency bands. It has a broad band antenna, a local oscillator, mixer diodes, amplifiers and processing circuitry. The local oscillator frequency is mixed with radar signal from the antenna to produce an intermediate signal which is then amplified, converted detected and fed to signal processing circuitry (cf. U.S. Pat. No. 4,961,074, Martinson).
On the other hand a common type of a Doppler radar device is one that emits a continuous wave radio signal at preset frequency which is kept stable and monitors return of the reflected signal from the target. It has a narrow band antenna with high gain and tight radiation pattern, at least one mixer diode, amplifiers and processing circuitry. Travelling signal frequency changes when the signal is reflected of a target with exact change of frequency corresponding to the relative speed of the target.
Returned signal is mixed with the radar oscillator signal to produce an intermediate signal which is in this case same as the frequency shift caused by the reflection from a moving target. Frequency shift is processed by the processing circuitry and corresponding target speed is shown on the display of the unit (cf. U.S. Pat. No. 4,236,140, Aker). Radar engineers are aware that the radar signal can be detected by a radar detector device and many different ways have been implemented to avoid detection by a radar detector. First, more than one usual radar frequency was used, but radar detectors developed sweeping local oscillators that could scan a whole frequency band for a signal. Then higher frequency bands were used by radars that were multiple orders of magnitude higher than before, 10.250 MHz increased to 24.150 MHz and 34.300 MHz. In time technological advance of radar detectors made them able of sweeping even those higher frequency bands.
Then a range of possible preset radar frequencies within the frequency band was made extremely wide, 33.400 MHz to 36.000 MHZ. That made the sweeping of a radar detector in that band a long process, the accuracy of radar detection was low and the time it took to detect made it unusable.
Improved radar detectors could concentrate sweeping only to those areas of the super wide band that the radars used most often. Some radar detector devices have the possibility for its user to select which frequency sub-bands to sweep and which not to.
Finally some Doppler radar engineers developed a burst continuous wave radar. Since Doppler target speed measurement depends on the stable frequency of the transmitted radio signal a frequency hopping or sweeping methods can not be used because that would degrade the accuracy of the radar. One manufacturer developed a short burst CW radar, so called BEE III POP Mode™ radar. Time required for a valid target speed to be measured by this radar type is shorter than 67 ms and this radar never transmits its signal longer than 67 ms at a time. Between each measurement is an off period which makes it difficult for a radar detector to confirm the presence of a radar. At that time Radar detectors have usually confirmed the sweeping detection of a radar several times before considering the result as true.
To counter to this type of a radar, one radar detector has developed an advanced method to discriminate between false readings and short burst CW radar signal. Upon initial detection of a radar signal, sweeping of the local oscillator is focused on the frequency segment where the signal was found instead of continuing the sweep to the end of its range. Focused sweeping will either confirm the presence of a radar in relatively short time or it will conclude that it is not a radar signal in which case the local oscillator will be returned to the original sweep of the frequency range (cf. U.S. Pat. No. 7,215,276, Batten).
This gradual technological development of both the Doppler radar device and the radar detector device has led to them being a far more complex devices then before. Radar devices are usually manufactured by specialized manufacturers according to military and police specifications and production quantities are usually small. Thus the quality control for each manufactured device can be thorough resulting in high rate of fault detection by the manufacturer himself. Requirements of the military standard that usually applies to such radar devices additionally contribute to increased durability and a fault immune design. For those reasons a relatively small number of devices that exhibit some kind of a manufacturing fault is expected to reach users or distributors of such devices.
Contrary to Doppler radars a radar detector devices are manufactured by great many manufacturers. Many of which also manufacture other unrelated electronic products thus lowering the expected quality of the devices design. Radar detector devices are usually manufactured in large quantities often larger than 100.000 devices per year. It is also expected that users of a radar detector device will have limited funds when acquiring the device so manufacturers have to limit the device's research, manufacturing and quality control costs. For the mentioned reasons it is expected that significant number of manufactured devices will have some kind of manufacturing fault that will not be detected by the quality control of the manufacturer or that the devices will exhibit a fault during use.
Resolving the problem of a faulty radar detector devices reaching users is possible by additional quality controls performed by distributors of such devices or manufacturers additionally testing the devices. If a user finds a device to be faulty or questionable it needs to be properly tested at appropriate service locations using a radar detector calibrator device.
Besides testing the device's user interface for proper operation it is essential that device's main function is properly tested, detecting of a radar signal. Having a Doppler radar or more accurately all different kinds of Doppler radars and setting them up in different ways to test the radar detector device for a proper radar signal detection is not convenient or even always possible. That is why a radar signal is usually emulated to perform a radar detector main function testing.
Prior art radar detector calibrators are microwave frequency generators that generate a stable frequency CW signal in a frequency range up to 40 GHz or higher. Emulation of a radar signal is achieved by simply entering the desired output frequency on the microwave generator. Some microwave generators even have possibility of altering the output signal power and some have the possibility of transmitting a burst CW signals.
Testing a radar detector device with these prior art calibrators translates into a radar detector device detecting or not the selected frequency signal from the microwave generator.
How ever, situations in which a radar detector device will be used by the user do not resemble the described situation where a stable frequency signal is presented to the device. Usual encounter of a radar signal by the radar detector device in the field will more closely resemble a very weak signal slowly growing in strength with occasional strong interference signal from other microwave source.
The signal will also possibly be a 67 ms burst CW signal. Also a usual encounter would be a several reflected radar signals coming to a radar detector device from different directions at the same time.
Such complex emulations are hard to achieve even with several microwave generators and it would be required of them to be used in the field what is rarely possible with such expensive professional equipment.
The present invention overcomes the observed problems in the radar detector quality assessment in the segment of complete and true main function testing.